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Summary Autoimmune inner ear disease is characterized by progressive, bilateral although asymmetric, sensorineural hearing loss. Patients with autoimmune inner ear disease had higher frequencies of interferon‐γ‐producing T cells than did control subjects tested. Human adipose‐derived mesenchymal stem cells (hASCs) were recently found to suppress effector T cells and inflammatory responses and therefore have beneficial effects in various autoimmune diseases. The aim of this study was to examine the immunosuppressive activity of hASCs on autoreactive T cells from the experimental autoimmune hearing loss (EAHL) murine model. Female BALB/c mice underwent β‐tubulin immunization to develop EAHL; mice with EAHL were given hASCs or PBS intraperitoneally once a week for 6 consecutive weeks. Auditory brainstem responses were examined over time. The T helper type 1 (Th1)/Th17‐mediated autoreactive responses were examined by determining the proliferative response and cytokine profile of splenocytes stimulated with β‐tubulin. The frequency of regulatory T (Treg) cells and their suppressive capacity on autoreactive T cells were also determined. Systemic infusion of hASCs significantly improved hearing function and protected hair cells in established EAHL. The hASCs decreased the proliferation of antigen‐specific Th1/Th17 cells and induced the production of anti‐inflammatory cytokine interleukin‐10 in splenocytes. They also induced the generation of antigen‐specific CD4+ CD25+ Foxp3+  Treg cells with the capacity to suppress autoantigen‐specific T‐cell responses. The experiment demonstrated that hASCs are one of the important regulators of immune tolerance with the capacity to suppress effector T cells and to induce the generation of antigen‐specific Treg cells.

This paper provides a review of the literature on high‐frequency trading and discusses various initiatives taken by regulatory authorities around the world to address its potential detrimental effects on market quality and investor welfare. Empirical evidence to date generally suggests that high‐frequency trading has improved market quality during normal times. What is not clear is the role of high‐frequency traders during episodic periods of market crash and extreme volatility. A fruitful area of future research may be a comparative analysis of the role of high‐frequency traders and the efficacy of various regulatory initiatives across periods of varying market conditions.

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